The invention relates to a method for producing ends of metal of composite pipe lengths, particularly such pipe lengths comprising a casing pipe of metal and a load-carrying sheath of reinforced plastics, which sheath is produced by applying reinforcement onto said casing pipe and filling said reinforcement with resin through injection under vacuum by pipes or cannulas, said reinforcement preferably comprising a first reinforcement layer closest to the casing pipe for carrying peripheral loads and a second reinforcement layer on the outside of the first-mentioned reinforcement layer for carrying axial loads on the pipe.
There is today no known techniques for producing ends of metal of such composite pipe lengths, which ends are intended to be joined at each other by known and classified techniques to form a pipeline of great length. Said pipeline has to withstand large pressure and high temperature. Such pipelines are intended for production and transportation of i.e. natural gas and oil.
Therefore, the object of the invention is to suggest a method for producing ends of metal of composite pipe lengths, which ends can be joined together by known and classified techniques, for instance by welding or a flange coupling.
This object is achieved according to the invention in that a sleeve of preferably the same metal as the casing pipe and with the same thickness of material as the first reinforcement layer is attached to the casing pipe at both ends of said casing pipe, wherein at least one of said sleeves are provided with axial through holes for injection pipes and vacuum connections, that the first reinforcement layer is applied thereafter to the same thickness of material as the sleeves over the whole length of the casing pipe between the sleeves and placing successively at the same time said injection pipes in parallel relationship to the longitudinal axis of the casing pipe, that a sheet metal strip of preferably the same metal as said casing pipe and with a greater width than the axial length of the sleeves is attached to said sleeves, respectively, and wound together with the second reinforcement layer onto the sleeves as well as onto a part of the first reinforcement layer, the sheet metal strip having a steplike reduced thickness in the direction of its width to a depth corresponding to the thickness of material of the second reinforcement layer, so that said second reinforcement layer will be placed between the winding layers of the sheet metal strip, while the part of the winding layers of the sheet metal strip not being stepped will lie upon each other without any intermediate reinforcement, forming an end surface totally of metal at the pipe length, the pipe length then being finished by injection of a suitable polymer in both reinforcement layers.